Methods of generating electricity

History

Central power stations became economically practical with the development of alternating current power transmission, using power transformers to transmit power at high voltage and with low loss. Electricity has been generated at central stations since 1882. The first power plants were run on water power^[2] or coal,^[3] and today we rely mainly on coal, nuclear, natural gas, hydroelectric, wind generators, and petroleum, with a small amount from solar energy, tidal power, and geothermal sources.

The use of power-lines and power-poles have been significantly important in the distribution of electricity.

Cogeneration

Cogeneration is the practice of using exhaust or extracted steam from a turbine for heating purposes, such as drying paper, distilling petroleum in a refinery or for building heat. Before central power stations were widely introduced it was common for industries, large hotels and commercial buildings to generate their own power and use low pressure exhaust steam for heating. This practice carried on for many years after central stations became common and is still in use in many industries.

Methods of generating electricity

There are seven fundamental methods of directly transforming other forms of energy into electrical energy:

· Static electricity, from the physical separation and transport of charge (examples: triboelectric effect and lightning)

· Electromagnetic induction, where an electrical generator, dynamo or alternator transforms kinetic energy (energy of motion) into electricity. This is the most used form for generating electricity and is based on Faraday's law. It can be experimented by simply rotating a magnet within closed loops of a conducting material (e.g. copper wire)

· Electrochemistry, the direct transformation of chemical energy into electricity, as in a battery, fuel cell or nerve impulse

· Photoelectric effect, the transformation of light into electrical energy, as in solar cells

· Thermoelectric effect, the direct conversion of temperature differences to electricity, as in thermocouples, thermopiles, and thermionic converters.

· Piezoelectric effect, from the mechanical strain of electrically anisotropic molecules or crystals. Researchers at the US Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a piezoelectricgenerator sufficient to operate a liquid crystal display using thin films of M13 bacteriophage.^[7]

· Nuclear transformation, the creation and acceleration of charged particles (examples: betavoltaics or alpha particle emission)

Static electricity was the first form discovered and investigated, and the electrostatic generator is still used even in modern devices such as the Van de Graaff generator and MHD generators. Charge carriers are separated and physically transported to a position of increased electric potential.

Almost all commercial electrical generation is done using electromagnetic induction, in which mechanical energy forces an electrical generator to rotate. There are many different methods of developing the mechanical energy, includingheat engines, hydro, wind and tidal power.

The direct conversion of nuclear potential energy to electricity by beta decay is used only on a small scale. In a full-size nuclear power plant, the heat of a nuclear reaction is used to run a heat engine. This drives a generator, which converts mechanical energy into electricity by magnetic induction.

Most electric generation is driven by heat engines. The combustion of fossil fuels supplies most of the heat to these engines, with a significant fraction from nuclear fission and some from renewable sources. The modern steam turbine(invented by Sir Charles Parsons in 1884) currently generates about 80% of the electric power in the world using a variety of heat sources.

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